THE VARIATION OF SMALL DISTURBANCE WITH THE MULTIPURPOSE DAM IN JAPANESE RESERVOIRS

Abstract

Variation of small disturbance regime is investigated in 100 Japanese dam reservoir. Natural flow disturbance is large in spring-summer and small in autumn-winter. The disturbance can classify the dam into three types(The North East type, The South type, The Middle type).The North East type is large in spring, and The South type is large in summer. The reservoir operations tend to depress the flow disturbance of spring. And the operations tend to press up it of winter. Urban water demands lead to flatter hydrographs as one can imagine, but irrigation and hydropower caused complex effects on flow regimes. By the newly proposed rule, the influence of the dam operation was improved in spring but was not improved in winter.